1. A physical quantity is a quantity that can be measured.

2. Physical quantities are measured in S.I. units. a. S.I. units means International System of

Units.

i. The unit metre(m) is used for measuring length. ii. Long distance such as the distance between two towns are measured in kilometres.(km)

i. Time is measured in seconds. ii. Other units for time are minutes, hours, days, weeks and months

i. Mass is the total content of matter in an object. ii. Mass is measured in kilogram. iii. Small masses are usually measured in grams or milligrams. iv. Large masses are measured in tonnes.

i. Temperature is the degree of hotness or coldness. ii. The S.I. unit for temperature is Kelvin. iii. Other units for temperature are the metric unit degrees Celsius or degrees Fahrenheit. iv. Our body temperature is measured using a clinical thermometer. The scale on the thermometer from 32 oC to 42oC.

i. Electric current is the flow of electrons.

ii. It is measured using an ammeter. iii. Electric current is measured in ampere

Reference book

1. Prefixes are useful in expressing physical quantities that are either too big or too small. 2. For example, the thickness of a book is measured in centimetres where centi- is the prefix added to metre to express a smaller value. 3. A prefix is added to change the value of the unit. 4. Hence, the value of any physical quantity can be changed to prefix form.

Length is the distance between two points. 2. The length of an object can be measured using a metre rule . 3. The length of a metre rule is one metre. 4. distance also can be measured using measuring tape

a. The ruler is placed at the side of the object to be measured. b. To take a reading, your eye needs to be vertically above the end of the object (position B) as shown in.

c. If the position of the eye is at A or C, the reading taken is not accurate. d. This error is known as parallax error. e. The length is measured by taking several readings and the average length is then determined.

a. Some thread and a ruler are used for measuring the length of a curve. b. The thread is placed along the length of the curve PQ. The end of the curve is marked on the thread. c. The length of the thread is later measured using the metre rule. d. The length of the curve is measured three times. Then average length is determined.

e. The length of the curve PQ can also be measured using an opisometer and a metre rule.

thermometer

a. The inner and outer diameters of round objects can be measured using calipers and a ruler. b. External calipers are used to measure the external diameter of the object. c. Internal calipers are used to measure the internal diameter of the object.

1. The S.I. unit for area is square metres (m2).

2. A huge area can be measured in square kilometres whereas for smaller areas are measured in square centimetres (cm2) and square millimetres (mm2).a. 1 m2 = 10 000 cm2 b. 1 cm2 = 100 mm2 3. The area of objects with regular shapes are calculated using mathematical formulae.

4. The area of irregular-shaped objects can be estimated by using graph paper

a. The shape of the object is traced on a graph paper. b. Tick ( ) for every complete square (measuring 1 cm2 ) covered by the object. c. Then tick ( ) the squares where the area is half or more than half the area of the square.

d. The total number of ( ) on the graph paper for the shape is counted

1. The S.I. unit for volume is cubic metres (m3). 2. Other units for volume is cubic millimetres (mm3 ), cubic centimetres (cm3 ), millilitres (ml) and litre (l). 3. The volume of liquids is usually measured in litre and millilitre. 4. The volume of solids is measured in cm3 and m3 units.

5. measuring cylinder, burette and pipette can be use to measure the volume of liquid 6. The level of the liquid in a measuring cylinder is curved downwards. This curve is called the meniscus. 7. When reading the volume, the reading should be taken at the same level as the bottom of the meniscus. 8. The correct eye position prevents parallax error.

a. The volume of regular solids and irregular solids can be measured by using the water displacement method. b. The eureka can used to measure the volume of regular and irregular solids.

1. Earths gravity pulls all objects to its centre. 2. The weight of an object is a result of the force of gravity.

3. The weight of an object is not constant . It changes from one place to another depending on the force of gravity. 4. The weight of an object is greater at the poles than at the equator.

5. The weight of an object can be measured using a spring balance or a compression balance. 6. The S.I. unit for measuring weight is newton (N). 7. One newton is almost equal to one tenth (1/10) of a kilogram-force.

1. Mass is the quantity of matter contained in an object. 2. The mass of an object does not change because the quantity of matter contained in it is the same wherever the object is. 3. beam balance, lever balance and electronic balance is used to measure mass

Reference book

A. standard system of units is important to create better understanding between countries in trading, international transportation and scientific research. B. Before S.I. units were introduced in 1960, B. Before S.I. units were introduced in 1960, other systems of standard units were used such as the system of footpound- pound-second (FPS). C. The metric system of measurement is now a common standard of measurement and it is used as S.I. units.